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Abstract:

A safety device for a machine having an action part for processing or
moving an object includes: a posture obtainment unit configured to obtain
a plurality of posture data indicating a posture of at least part of the
lower body of a worker; and a preparatory movement determination unit
configured to determine that a preparatory movement preceding a dangerous
movement which brings at least part of the upper body of the worker
closer to a working area of the action part is being performed in the
case where a change in the posture indicated by the plurality of posture
data shows that the worker is shifting a center of gravity of whole body
of the worker in an orientation away from the working area of the action
part without changing positions of both feet.

Claims:

1. A safety device for a machine having an action part for processing or
moving an object, said safety device comprising: a posture obtainment
unit configured to obtain a plurality of posture data indicating a
posture of at least a part of a lower body of a worker; and a preparatory
movement determination unit configured to determine that a preparatory
movement preceding a dangerous movement is being performed in the case
where a change in the posture indicated by the plurality of posture data
shows that the worker is shifting a center of gravity of whole body of
the worker in an orientation away from a working area of the action part
without changing positions of both feet, the dangerous movement being a
movement of at least a part of an upper body of the worker approaching
the working area of the action part.

2. The safety device according to claim 1, wherein the plurality of
posture data include a pressure distribution of soles of feet of the
worker, and said preparatory movement determination unit is configured to
determine that the preparatory movement is being performed in the case
where a position specified by the pressure distribution is moving in an
orientation away from the working area of the action part.

3. The safety device according to claim 2, wherein the position specified
by the pressure distribution is a center-of-gravity position of the
pressure distribution.

4. The safety device according to claim 3, wherein said preparatory
movement determination unit is configured to determine that the
preparatory movement is being performed in the case where the
center-of-gravity position is shifting in the orientation away from the
working area of the action part and a moving speed, a moving time, or a
moving distance of the center-of-gravity position in the orientation away
from the working area of the action part is greater than or equal to a
first threshold value.

5. The safety device according to claim 4, wherein said preparatory
movement determination unit is configured to determine that the
preparatory movement is being performed in the case where the
center-of-gravity position is shifting in an orientation away from the
working area of the action part and a moving speed, a moving time, or a
moving distance of the center-of-gravity position in the orientation away
from the working area of the action part is from greater than or equal to
the first threshold value to less than a second threshold value.

6. The safety device according to claim 3, further comprising a distance
detection unit configured to detect a distance between the working area
of the action part and the worker, wherein said preparatory movement
determination unit is configured to determine that the preparatory
movement is being performed in the case where the center-of-gravity
position is shifting in an orientation away from the working area of the
action part and the distance is less than a third threshold value.

7. The safety device according to claim 6, further comprising: a size
detection unit configured to detect a size of at least a part of the body
of the worker; and a correction unit configured to correct the detected
distance such that when the size of the at least a part of the body of
the worker is larger, the distance is shorter, wherein said preparatory
movement determination unit is configured to determine that the
preparatory movement is being performed in the case where the
center-of-gravity position is shifting in the orientation away from the
working area of the action part and the corrected distance is less than
the third threshold value.

8. The safety device according to claim 3, further comprising an
orientation detection unit configured to detect a body orientation of the
worker, wherein said preparatory movement determination unit is
configured to determine that the preparatory movement is being performed
in the case where the center-of-gravity position is shifting in an
orientation away from the working area of the action part and an angle
formed between the body orientation of the worker and an orientation of
the working area of the action part seen from the worker is within a
predetermined range.

9. The safety device according to claim 3, further comprising a
preparatory movement definition storage unit configured to store a first
threshold value, wherein said preparatory movement determination unit is
configured to determine that the preparatory movement is being performed
in the case where the center-of-gravity position is shifting in an
orientation away from the working area of the action part, and a moving
speed, a moving time, or a moving distance of the center-of-gravity
position in the orientation away from the working area of the action part
is greater than or equal to the stored first threshold value.

10. The safety device according to claim 9, further comprising a distance
detection unit configured to detect the distance between the working area
of the action part and the worker, wherein said preparatory movement
definition storage unit is configured to store a plurality of first
threshold values including the first threshold value in association with
distances between the working of the action part area and the worker, and
said preparatory movement determination unit is configured to (i) specify
a first threshold value corresponding to the detected distance among the
plurality of the first threshold values stored in said preparatory
movement definition storage unit and (ii) determine that the preparatory
movement is being performed in the case where the center-of-gravity
position is shifting in an orientation away from the working area of the
action part, and a moving speed, a moving time, or a moving distance of
the center-of-gravity position in the orientation away from the working
area of the action part is greater than or equal to the specified first
threshold value.

11. The safety device according to claim 10, further comprising: a size
detection unit configured to detect a size of the soles of feet of the
worker based on the pressure distribution; and a correction unit
configured to correct the detected distance such that when the size of
the soles of feet of the worker is larger, the distance is shorter,
wherein said preparatory movement determination unit is configured to
specify the first threshold value corresponding to the corrected distance
among the plurality of the first threshold values.

12. The safety device according to claim 2, wherein said posture
obtainment unit is configured to obtain, from a pressure sensor installed
on a floor surface, the plurality of posture data including the pressure
distribution of the soles of feet of the worker.

13. The safety device according to claim 1, further comprising a safety
operation control unit configured to slow down or stop the action part in
the case where it is determined that the preparatory movement is being
performed.

14. A preparatory movement determination method for preventing a worker
from being injured by a machine having an action part for processing or
moving an object, said preparatory movement determination method
comprising: obtaining a plurality of posture data indicating a posture of
at least a part of a lower body of the worker; and determining that a
preparatory movement preceding a dangerous movement is being performed in
the case where a change in the posture indicated by the plurality of
posture data shows that the worker is shifting a center of gravity of
whole body of the worker in an orientation away from a working area of
the action part without moving positions of both feet, the dangerous
movement being a movement of at least a part of an upper body of the
worker approaching the working area of the action part.

15. A non-transitory computer-readable recording medium having a program
recorded thereon for causing a computer to execute the preparatory
movement determination method according to claim 14.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation application of PCT Patent Application No.
PCT/JP2011/006443 filed on Nov. 18, 2011, designating the United States
of America, which is based on and claims priority of Japanese Patent
Application No. 2011-007349 filed on Jan. 17, 2011. The entire
disclosures of the above-identified applications, including the
specifications, drawings and claims are incorporated herein by reference
in their entirety.

TECHNICAL FIELD

[0002] Devices and methods consistent with one or more exemplary
embodiments of the present disclosure relate generally to a safety device
and a preparatory movement determination method of preventing an accident
in which a worker's body is caught in an action part during operation of
a machine having the action part, or the like.

BACKGROUND ART

[0003] There is a growing need for a machine press which presses a work
object to operate safely. For example, there is a growing need for a
technique to stop operation of the machine press when it detects that
part of a worker's body has entered an area in which an action part of
the machine press operates (dangerous area).

[0004] FIGS. 1A and 1B each show an example of an action part of an
electrical machine press according to Patent Literature 1. FIG. 1A is an
elevation view of the action part of the electrical machine press.
Moreover, FIG. 1B is a left side view of the action part of the
electrical machine press.

[0005] An upper mold 7 is mounted under an upper slide 3, while a lower
mold 9 is mounted on a lower slide 5. Hereafter, the upper slide 3 and
the lower slide 5 are referred to as the upper and lower slides or only
the slides. A work object W is disposed between the upper mold 7 and the
lower mold 9. Then, a distance between the upper mold 7 and the lower
mold 9 is decreased. As a result, pressure is applied to the work object
W and the work object W is processed. The upper slide 3, the lower slide
5, the upper mold 7, and the lower mold 9 are components for processing
the work object W, all of which correspond to the action part.

[0006] For example, the worker causes a hand to enter between the upper
and lower slides from a front plane in FIG. 1A, that is, from a right
side in FIG. 1B in order to replace the work object or determine a
position of the work object. A region in which a hand is likely to be
caught (dangerous area) is a position sandwiched between the upper mold 7
and the lower mold 9.

[0007] In a conventional machine press, a worker prevents a hand from
being caught in the machine through manually cutting off power when a
work for replacing the work object or determining the position of the
work object is performed. Moreover, a machine press according to Patent
Literature 2 prevents a hand of a worker from being caught, in the
machine by automatically cutting off power based on detection by an entry
detection sensor, an area sensor, or the like that part or the whole of
the worker's body has entered a dangerous area.

[0010] However, the above described conventional techniques have
difficulties in preventing a decrease in working efficiency and ensuring
an increase in safety.

[0011] Therefore, the present disclosure relates to a safety device
provided with an aim to prevent a decrease in working efficiency and
ensure an increase in safety.

Solution to Problem

[0012] In order to achieve the object, a safety device according to an
aspect of the present disclosure is a safety device for a machine having
an action part for processing or moving an object, including: a posture
obtainment unit configured to obtain a plurality of posture data
indicating a posture of at least a part of a lower body of a worker; and
a preparatory movement determination unit configured to determine that a
preparatory movement preceding a dangerous movement is being performed in
the case where a change in the posture indicated by the plurality of
posture data shows that the worker is shifting a center of gravity of
whole body in an orientation away from a working area of the action part
without changing positions of both feet, the dangerous movement being a
movement of at least a part of an upper body of the worker approaching
the working area of the action part.

[0013] It should be noted that these overall and specific aspects may be
implemented as a system, a method, an integrated circuit, a computer
program, or a recording medium, and as an optional combination of a
system, a method, an integrated circuit, a computer program, and a
recording medium.

Advantageous Effects of Invention

[0014] Exemplary devices and methods in the present disclosure and their
equivalents within the scope of the inventive concept defined in the
attached claims make it possible to provide a safety device which can
prevent a decrease in working efficiency and ensure an increase in
safety.

BRIEF DESCRIPTION OF DRAWINGS

[0015] These and other advantages and features of exemplary embodiments of
the present disclosure will become apparent from the following
description thereof taken in conjunction with the accompanying Drawings
that illustrate general and specific exemplary embodiments of the present
disclosure. In the Drawings:

[0016] FIG. 1A is an elevation view of an action part of a conventional
machine press;

[0017] FIG. 1B is a left side view of the action part of the conventional
machine press;

[0020]FIG. 4 is a block diagram showing a functional configuration of a
safety device according to Embodiment 1 of the present disclosure;

[0021]FIG. 5A is a diagram showing a scene in which a worker is setting a
work object on a pressing position;

[0022]FIG. 5B is a diagram showing a scene in which the machine press is
processing the work object;

[0023]FIG. 6 is a diagram for explaining a preparatory movement preceding
a dangerous movement.

[0024]FIG. 7 is a diagram showing an example of a pressure sensor sheet
according to Embodiment 1;

[0025]FIG. 8 is a diagram showing an example of a pressure value measured
by the pressure sensor sheet according to Embodiment 1;

[0026] FIG. 9 is a diagram showing an example of a preparatory movement
definition table according to Embodiment 1;

[0027]FIG. 10 is a diagram showing an example of a shift of a
center-of-gravity position according to Embodiment 1;

[0028]FIG. 11 is a flowchart showing operations of the safety device
according to Embodiment 1;

[0029]FIG. 12 is a diagram showing a scene in which a worker is setting a
work object on a pressing position;

[0030]FIG. 13 is a block diagram showing a functional configuration of a
safety device according to Embodiment 2 of the present disclosure;

[0031]FIG. 14 is a diagram showing an example of a pressure sensor sheet
according to Embodiment 2;

[0032]FIG. 15 is a diagram showing another example of the pressure sensor
sheet according to Embodiment 2;

[0033] FIG. 16 is a diagram showing an example of a preparatory movement
definition table according to Embodiment 2;

[0034] FIG. 17 is a flowchart showing operations of the safety device
according to Embodiment 2;

[0035]FIG. 18 is a diagram showing a scene in which a worker and a robot
are carrying out cooperative transportation; and

[0036]FIG. 19 is a block diagram showing a functional configuration of a
safety device according to an aspect of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Underlying Knowledge Forming Basis of the Present Disclosure

[0037] The inventors found that the following problems occur in the
detection of an entry into a dangerous area as described in the
Background Art.

[0038] As an entry detection sensor for detecting an entry into a
dangerous area, for example, a beam sensor using an infrared ray or the
like is used. The entry detection sensor is, for example, is installed
just before a dangerous area (a movable area of the slides of FIG. 1, for
example). The machine press prevents a worker's body from being caught
between molds by stopping the slides on the detection that the body
passes through the position of the entry detection sensor.

[0039] In the case where the entry detection sensor is installed on a
borderline of the dangerous area, the time is short between when the
worker's body passes through the installation position of the entry
detection sensor and when the worker's body reaches the dangerous area,
with a result that the suspension of the slides is too late. Therefore,
the entry detection sensor is installed at a position a predetermined
distance away from the dangerous area. Specifically, the entry detection
sensor is installed at a position farther away from the dangerous area
than a distance covered by the body between when the entry detection
sensor detects the passage of the body at the installment position of the
entry detection sensor and when the slides of the machine press make a
full stop. With this, in the case where the worker moves fast or in the
case where long time is needed for the action part to make a full stop,
the worker's body can be prevented from being caught in the action part.

[0040] However, the entry detection sensor must be installed at a position
a predetermined distance away from the dangerous area. Especially, in the
case where necessary time to fully stop the slides in operation is long
or in the case where the worker's body movement is fast, the entry
detection sensor must be installed at a position a large distance away
from the dangerous area.

[0041] In this case, the possibility is high that even if the worker's
body passes through the position of the entry detection sensor, the body
will not enter the dangerous area. In other words, there has been a
problem that the possibility is high that the slides are erroneously
stopped with a result that working efficiency is decreased.

[0042] In order to achieve the object, a safety device according to an
aspect of the present disclosure is a safety device for a machine having
an action part for processing or moving an object, including: a posture
obtainment unit configured to obtain a plurality of posture data
indicating a posture of at least a part of a lower body of a worker; and
a preparatory movement determination unit configured to determine that a
preparatory movement preceding a dangerous movement is being performed in
the case where a change in the posture indicated by the plurality of
posture data shows that the worker is shifting a center of gravity of
whole body of the worker in an orientation away from a working area of
the action part without changing positions of both feet, the dangerous
movement being a movement of at least a part of an upper body of the
worker approaching the working area of the action part.

[0043] With this configuration, it can be determined that a preparatory
movement is being performed which precedes a dangerous movement of the
upper body of the worker approaching the working area of the action part,
by using a change in the posture of the lower body of the worker. The
preparatory movement is a movement unintentionally performed by a person
before the person performs a conscious movement. In other words, the
worker unintentionally performs the preparatory movement before a
dangerous movement that is a conscious movement. Therefore, by
determining that the preparatory movement is being performed, it is
possible to detect with high accuracy that the dangerous movement is
performed before the dangerous movement is performed. As a result, the
present disclosure can prevent a decrease in working efficiency and
ensure an increase in safety.

[0044] For example, the plurality of posture data may include a pressure
distribution of soles of feet of the worker, and the preparatory movement
determination unit may be configured to determine that the preparatory
movement is being performed in the case where a position specified by the
pressure distribution is moving in an orientation away from the working
area of the action part.

[0045] With this configuration, it can be determined whether or not the
preparatory movement is being performed, by using the position specified
by the pressure distribution of the soles of feet of the worker. In other
words, it is possible to detect that the worker is shifting the center of
gravity of whole body of the worker in an orientation away from the
working area of the action part, by using the shift of the position
specified by the pressure distribution of the soles of feet of the
worker. Therefore, it is possible to determine with relative ease that
the preparatory movement preceding the dangerous movement is being
performed.

[0046] For example, the position specified by the pressure distribution
may be a center-of-gravity position of the pressure distribution.

[0047] With this configuration, it can be determined whether or not the
preparatory movement is being performed, by using the center-of-gravity
position of the pressure distribution of the soles of feet of the worker.
The preparatory movement is a movement for controlling a posture and
therefore is accompanied by a shift of the center of gravity of whole
body of the worker. Therefore, it is possible to determine with higher
accuracy that the preparatory movement preceding the dangerous movement
is being performed by using the center-of-gravity position of the
pressure distribution of the soles of feet of the worker.

[0048] For example, the preparatory movement determination unit may be
configured to determine that the preparatory movement is being performed
in the case where the center-of-gravity position is shifting in the
orientation away from the working area of the action part and a moving
speed, a moving time, or a moving distance of the center-of-gravity
position in the orientation away from the working area of the action part
is greater than or equal to a first threshold value.

[0049] With this configuration, it can be determined that the preparatory
movement is being performed in the case where a moving speed, a moving
time, or a moving distance of the center-of-gravity position in an
orientation away from the working area of the action part is greater than
or equal to the first threshold value. In other words, it is possible to
prevent an erroneous determination of the preparatory movement in the
case where the shift of the center-of-gravity position in an orientation
away from the working area of the action part is a small shift different
from the shift caused by the preparatory movement. Therefore, it is
possible to determine with higher accuracy that the preparatory movement
preceding the dangerous movement is being performed.

[0050] For example, the preparatory movement determination unit may be
configured to determine that the preparatory movement is being performed
in the case where the center-of-gravity position is shifting in an
orientation away from the working area of the action part and a moving
speed, a moving time, or a moving distance of the center-of-gravity
position in the orientation away from the working area of the action part
is from greater than or equal to the first threshold value to less than a
second threshold value.

[0051] With this configuration, it can be determined that the preparatory
movement is being performed in the case where a moving speed, a moving
time, or a moving distance of the center-of-gravity position in an
orientation away from the working area of the action part is less than
the second threshold value. In other words, it is possible to prevent an
erroneous determination of the preparatory movement in the case where the
shift of the center-of-gravity position in an orientation away from the
working area of the action part is a large shift different from the shift
caused by the preparatory movement. Therefore, it is possible to
determine with higher accuracy that the preparatory movement preceding
the dangerous movement is being performed.

[0052] For example, the safety device may further include a distance
detection unit configured to detect a distance between the working area
of the action part and the worker, wherein the preparatory movement
determination unit may be configured to determine that the preparatory
movement is being performed in the case where the center-of-gravity
position is shifting in an orientation away from the working area of the
action part and the distance is less than a third threshold value.

[0053] With this configuration, it can be determined that the preparatory
movement is being performed in the case where a distance between the
working area of the action part and the worker is less than the third
threshold value. In other words, since the possibility is low that the
worker's body enters the working area of the action part in the case
where the worker is at a position away from the working area of the
action part, it can be determined that the preparatory movement preceding
the dangerous movements is not being performed. To put it another way, in
the case where the possibility is low that the worker is injured, it is
possible to prevent the acting part from being stopped or slowed down and
to enhance workability.

[0054] For example, the safety device may further include a size detection
unit configured to detect a size of at least a part of the body of the
worker; and a correction unit configured to correct the detected distance
such that when the size of the at least a part of the body of the worker
is larger, the distance is shorter, wherein the preparatory movement
determination unit may be configured to determine that the preparatory
movement is being performed in the case where the center-of-gravity
position is shifting in the orientation away from the working area of the
action part and the corrected distance is less than the third threshold
value.

[0055] With this configuration, it is possible to correct a distance
between the working area of the action part and the worker such that when
a size of at least part of the body is larger, the distance is shorter.
The possibility is higher that the body enters the working area of the
action part when the body size of the worker is larger, even in the case
where the worker is at a position away from the working area of the
action part. Therefore, it is possible to determine with higher accuracy
that the preparatory movement preceding the dangerous movement is being
performed by determining whether or not the preparatory movement
preceding the dangerous movement is being performed with the use of a
distance corrected according to the body size of the worker.

[0056] For example, The safety device may further include an orientation
detection unit configured to detect a body orientation of the worker,
wherein the preparatory movement determination unit may be configured to
determine that the preparatory movement is being performed in the case
where the center-of-gravity position is shifting in an orientation away
from the working area of the action part and an angle formed between the
body orientation of the worker and an orientation of the working area of
the action part seen from the worker is within a predetermined range.

[0057] With this configuration, it can be determined whether or not the
preparatory movement is being performed with the use of the body
orientation of the worker. The possibility is high that the body enters
the working area of the action part when the orientation of the worker is
facing the front face of the machine. Therefore, it is possible to
determine with higher accuracy that the preparatory movement preceding
the dangerous movement is being performed.

[0058] For example, the safety device may further comprise a preparatory
movement definition storage unit configured to store a first threshold
value, wherein the preparatory movement determination unit may be
configured to determine that the preparatory movement is being performed
in the case where the center-of-gravity position is shifting in an
orientation away from the working area of the action part, and a moving
speed, a moving time, or a moving distance of the center-of-gravity
position in the orientation away from the working area of the action part
is greater than or equal to the stored first threshold value.

[0059] For example, the safety device may further include a distance
detection unit configured to detect the distance between the working area
of the action part and the worker, wherein the preparatory movement
definition storage unit may be configured to store a plurality of first
threshold values including the first threshold value in association with
distances between the working area of the action part and the worker, and
the preparatory movement determination unit is configured to (i) specify
a first threshold value corresponding to the detected distance among the
plurality of the first threshold values stored in the preparatory
movement definition storage unit and (ii) determine that the preparatory
movement is being performed in the case where the center-of-gravity
position is shifting in an orientation away from the working area of the
action part, and a moving speed, a moving time, or a moving distance of
the center-of-gravity position in the orientation away from the working
area of the action part is greater than or equal to the specified first
threshold value.

[0060] With this configuration, it can be determined whether or not the
preparatory movement is being performed with the use of the first
threshold value corresponding to the detected distance. The shift of the
center-of-gravity position in an orientation away from the working area
of the action part caused by the preparatory movement varies depending on
the distance between the working area of the action part and the worker.
For example, a moving distance of the center-of-gravity position is
longer because the dangerous movement is larger when the distance between
the working area of the action part and the worker is longer. Therefore,
it is possible to determine with higher accuracy that the preparatory
movement preceding the dangerous movement is being performed by
determining whether or not the preparatory movement is being performed
with the use of the first threshold value corresponding to the detected
distance.

[0061] For example, the safety device may further include: a size
detection unit configured to detect a size of the soles of feet of the
worker based on the pressure distribution; and a correction unit
configured to correct the detected distance such that when the size of
the soles of feet of the worker is larger, the distance is shorter,
wherein the preparatory movement determination unit may be configured to
specify the first threshold value corresponding to the corrected distance
among the plurality of the first threshold values.

[0062] With this configuration, it is possible to correct a distance
between the working area of the action part and the worker such that when
a size of at least part of the body is larger, the distance is shorter.
The possibility is higher that the body enters the working area of the
action part when the body size of the worker is larger, even in the case
where the worker is at a position away from the working area of the
action part. Therefore, it is possible to determine with higher accuracy
that the preparatory movement preceding the dangerous movement is being
performed by determining whether or not the preparatory movement
preceding the dangerous movement is being performed with the use of the
distance corrected according to the body size of the worker.

[0063] For example, the posture obtainment unit may be configured to
obtain, from a pressure sensor installed on a floor surface, the
plurality of posture data including the pressure distribution of the
soles of feet of the worker.

[0064] With this configuration, the pressure distribution of the soles of
feet of the worker can be measured with the use of the pressure sensor
installed on the floor surface.

[0065] For example, the safety device may further include a safety
operation control unit configured to slow down or stop the action part in
the case where it is determined that the preparatory movement is being
performed.

[0066] With this configuration, in the case where it is determined that
the preparatory movement is being performed, the acting part can be
stopped or be slowed down. Therefore, it is possible with more certainty
to prevent the worker from being injured.

[0067] It should be noted that these overall and specific aspects may be
implemented as a system, a method, an integrated circuit, a computer
program, a recording medium such as Compact Disk Read Only Memory
(CD-ROM), or the like, and as an optional combination of a system, a
method, an integrated circuit, a computer program, or a recording medium.

[0068] Hereafter, embodiments of the present disclosure will be described
in detail with reference to the drawings. It should be noted that all the
embodiments to be described later are specific examples of the present
disclosure. In other words, the numerical values, shapes, materials,
structural elements, the arrangement and connection of the structural
elements, steps, the processing order of the steps etc. shown in the
following exemplary embodiments are mere examples, and therefore do not
limit the inventive concept, the scope of which is defined in the
appended Claims and their equivalents. Therefore, among the structural
elements in the following exemplary embodiments, structural elements not
recited in any one of the independent claims defining the most generic
part of the inventive concept are not necessarily required to overcome
conventional disadvantages.

[0069] First, the terms of the body parts will be described with reference
to FIG. 2.

[0070]FIG. 2 is a diagram showing a human body seen from the back
surface. As shown in FIG. 2, the human body is divided into the upper
body and the lower body. The upper body includes the head region, the
cervical region, the back region, the buttock region, and the left and
right upper limbs.

[0071] The head region is a region supported by the skull and the
mandible, and includes the head and the face. Moreover, the head region
includes a region which includes all parts of the face such as eyes,
ears, a nose, a mouth, and the like. The cervical region is a portion of
the neck. The cervical region includes the first to the seventh vertebrae
and the peripheral region and is a region from the shoulder to the head
region. The back region is a dorsal region occupying the upper part of
the back surface of the trunk and is a region supported by rib bones. The
lumbar region is a region which is located in the lower part of the back
region of the lower part of the back surface of the trunk, and is a
region from the ribs to the pelvis. The left and right upper limbs
include left and right arms and hands.

[0072] The lower body is a region lower than the lumbar region and
includes left and right legs.

[0073] The left and right legs are parts lower than the hip joints. Each
of the left and right legs includes a femoral region and a leg. The
femoral region is a thigh. In other words, the femoral region is a part
higher than the knee of the leg. The foot region is a part lower than the
ankle.

[0074] Next, description about the preparatory movement will be made with
reference to FIG. 3.

[0075] The preparatory movement refers to an anticipatory postural
control. Specifically, the preparatory movement is defined as the
movement of the body as the posture of a person is controlled before a
motion of the person when the person tries to make the motion.

[0076] For example, in the case where a person stands on both legs and
lifts the right leg, the person shifts the center of gravity of whole
body to the left leg before lifting the right leg so that the person does
not fall even when the right foot is lifted. When such a motion is made,
the postural control which is done anticipatorily before the motion in
order to maintain the balance of the person's body is called the
preparatory movement.

[0077] Such a preparatory movement is unintentionally performed. The
preparatory movement is made several hundreds milliseconds before the
actual motion though depending on the body part to be used for the motion
or the scale of the motion (For example, refer to Reference Literature 1
(Atsushi Fujita, "Undou Shihai no Seiri Shinri: Undou Hannou no
Mekanizumu (Physiological Psychology of Exercise Control: Mechanism of
Exercise Response)", Chapter 2, p 15-22, "Shin-ban Undou Shinri-gaku
Nyumon" (New Edition--Introduction to Exercise Psychology) edited by Iwao
Matsuda and Takashi Sugihara, Taishukan Shoten, Tokyo, 1987).

[0078]FIG. 3 is a diagram for explaining a preparatory movement.
Specifically, FIG. 3 is a diagram in which description is added to the
drawings (FIGS. 2-8) illustrated in Reference Literature 1.

[0079] In Reference Literature 1, FIG. 3 is described as follows:
"selective reaction condition is set in such a manner that a subject
makes a systemic high jump or a low jump according to a light stimulus of
an upward or downward arrow randomly displayed on the right or left; a
response curve indicating the change in the distortion of a jumping board
caused by the subject's reaction, E.O.G. (electrooculogram) indicating
the corneoretinal potential due to the eye movement of the subject, and
E.M.G. (electromyogram) indicating the tension change in anterior tibial
muscle and gastrocnemius muscle of the subject are simultaneously
recorded on an oscillograph; and based on the recorded changes, the
reaction times are classified as I: latency of eye movement, II: eye
movement as time, III: decision time, IV: muscle contraction time V:
reaction time, VI: latency of leg flexion, or VII: jumping time."

[0080] As shown in the electromyogram (anterior tibial muscle and
gastrocnemius muscle) in FIG. 3, anterior tibial muscle as one of the
muscles of the shin moved before the movement of the gastrocnemius
muscle, which is a muscle in the calf used for making a jump. In other
words, before the movement of the gastrocnemius muscle, which is a body
part consciously used by a person to make a jump, the anterior tibial
muscle which is different from the body part is used for making a jump.
In this manner, by contraction of the anterior tibial muscle, the center
of gravity of the subject is slightly shifted forward. In other words, in
order to maintain the balance against backward shift of the center of
gravity caused by the contraction of the gastrocnemius muscle, forward
shift of the center of gravity is made as a preparatory movement.

[0081] Therefore, the use of such a preparatory movement allows for the
prediction of a dangerous movement before the movement is performed by
the worker. Therefore, in the following embodiments, the safety device
determines whether or not a preparatory movement is being performed which
precedes a dangerous movement which causes the worker to move the body
into the dangerous area.

[0082] Next, a machine tool which is an example of a machine will be
described. The machine tool is a machine which has an action part for
processing an object such as metal, stone, lumber, or the like (hereafter
described as a work object). The action part is a part which operates for
processing the work object. Specifically, the action part is a part which
is movable along with a part of which is in contact with the work object
and the contact part.

[0083] For example, the machine tool transforms the work object by a press
molding process by a mold, a rolling process by a roller, or a cutting
process by a drill, a blade, or a file.

[0084] In the case where the machine tool processes the work object, the
worker manually sets the work object on a position where the work object
can be processed, or manually corrects the position of the work object
which is automatically set. In this case, part of the upper body of the
worker (hands or the like) is located in an area where the action part of
the machine tool operates (hereafter referred to as working area or
dangerous area).

[0085] At this time, if the action part of the machine tool operates, part
of the upper body of the worker is in danger of being injured. For
example, in the case where the machine tool is a machine press, part of
the upper body of the worker is in danger of being caught in press molds.
Moreover, for example, in the case where the machine tool is a rolling
mill, part of the upper body of the worker is in danger of being caught
in rolling mill rollers. Furthermore, for example, in the case where the
machine tool is a cutter, part of the upper body of the worker is in
danger of being cut or trimmed by a drill, a blade, or a file.

[0086] Hereafter, descriptions will be made about a safety device which
prevents the worker from being injured by an action part of a machine
such as a machine tool.

Embodiment 1

[0087] A safety device 10 according to Embodiment 1 determines whether or
not a preparatory movement is being performed which precedes a dangerous
movement which causes part of the upper body of the worker to enter a
dangerous area. In the present embodiment, descriptions will be made, as
an example, about the case where the machine having the action part is a
machine tool (machine press).

[0088]FIG. 4 is a block diagram of the safety device 10 according to
Embodiment 1. As shown in FIG. 4, the safety device 10 includes a posture
obtainment unit 201, a preparatory movement definition storage unit 202,
a preparatory movement determination unit 203, an infrared sensor 204, an
entry detection unit 206, and a safety operation control unit 208. FIG. 4
further shows an action part 209 of a machine tool.

[0089] The posture obtainment unit 201 obtains a plurality of posture data
indicating a posture of at least part of the lower body of the worker. In
the present embodiment, the plurality of posture data includes a pressure
distribution of the soles of feet of the worker. More specifically, the
posture obtainment unit 201 obtains, as the plurality of posture data,
the pressure distribution of the soles of feet of the worker from a
plurality of pressure sensors installed on the floor surface.

[0090] The preparatory movement definition storage unit 202 is a storage
device having a storage area such as a non-volatile memory, a hard disk,
or the like. The preparatory movement definition storage unit 202 stores
a first threshold value and a second threshold value both of which are
used for determining whether or not the preparatory movement is being
performed.

[0091] The preparatory movement determination unit 203 determines, based
on a change in the posture indicated by the plurality of posture data,
whether or not the preparatory movement preceding the dangerous movement
is being performed. Specifically, the preparatory movement determination
unit 203 determines that the preparatory movement preceding the dangerous
movement is being performed in the case where the change in the posture
indicated by the plurality of posture data indicates that the worker is
shifting the center of gravity of whole body of the worker in an
orientation away from the working area of the action part 209. Then, the
preparatory movement determination unit 203 transmits the determination
result to the safety operation control unit 208.

[0092] Here, the dangerous movement is a movement of at least part of the
upper body of the worker approaching the working area of the action part
209. Moreover, the preparatory movement preceding the dangerous movement
is a movement performed by the worker before the dangerous movement. In
other words, the preparatory movement preceding the dangerous movement is
a movement for the worker to unintentionally control a posture before the
worker consciously performs the dangerous movement. In the present
embodiment, the preparatory movement is a movement for the worker to
shift the center of gravity of whole body of the worker in an orientation
away from the working area of the action part 209 without moving the
positions of both feet.

[0093] Moreover, the working area is an area in which the action part 209
operates and a dangerous area in which the worker is highly likely to be
injured.

[0094] In the present embodiment, the worker's shift in an orientation
away from the working area of the action part 209 without moving the
position of both feet corresponds to a shift of the position specified by
the pressure distribution of the soles of feet of the worker in an
orientation away from the working area of the action part. In other
words, the preparatory movement determination unit 203 determines that
the preparatory movement is being performed in the case where the
position specified by the pressure distribution is shifting in an
orientation away from the working area of the action part.

[0095] It should be noted that the position specified by the pressure
distribution is a center-of-gravity position of the pressure distribution
of the soles of feet. It should be noted that the position specified by
the pressure distribution does not necessarily have to be the
center-of-gravity position of the pressure distribution. For example, the
position specified by the pressure distribution may be the position at
which the highest pressure value is measured.

[0096] Furthermore, in the present embodiment, the preparatory movement
determination unit 203 determines whether or not the preparatory movement
preceding the dangerous movement is being performed, based on a moving
speed, a moving time, or a moving distance of the center-of-gravity
position in an orientation away from the working area of the action part.
In other words, the preparatory movement determination unit 203
determines that the preparatory movement is being performed in the case
where the center-of-gravity position of the pressure distribution is
shifting in an orientation away from the working area of the action part,
and a moving speed, a moving time, or a moving distance of the
center-of-gravity position in an orientation away from the working area
of the action part is from greater than or equal to the first threshold
value to less than the second threshold value. The first threshold value
and the second threshold value are stored in the preparatory movement
definition storage unit 202.

[0097] The infrared sensor 204 detects that the worker's body has entered
a detection area which includes the dangerous area and which is an area
greater than the dangerous area. Specifically, the infrared sensor 204
detects that the worker's body has entered the detection area by
detecting that an infrared ray has been blocked by the worker's body.
Then, the infrared sensor 204 transmits, to the entry detection unit 206,
a detection signal indicating the detection of the body of a worker 100.

[0098] It should be noted that the safety device 10 includes the infrared
sensor 204 in the present embodiment, but does not necessarily have to
include the infrared sensor 204. In other words, the safety device 10
does not necessarily have to detect the entry of the worker's body into
the detection area with the use of infrared ray. For example, the safety
device 10 may include an entry detection sensor for detecting the entry
of the body of the worker 100 into the detection area by capturing an
image of the detection area and by determining whether or not the
worker's body is included in the image.

[0099] The entry detection unit 206 determines that the worker's body is
entering the detection area in the case where a detection signal is
received from the infrared sensor 204. Then, the entry detection unit 206
transmits the determination result to the safety operation control unit
208.

[0100] The safety operation control unit 208 controls the action part 209.
Specifically, the safety operation control unit 208 stops the action part
209 in the case where it is determined by the entry detection unit 206
that the body of the worker 100 is entering a detection area 130.

[0101] Moreover, the safety operation control unit 208 slows down the
action part 209 in the case where it is determined by the preparatory
movement determination unit 203 that the preparatory movement preceding
the dangerous movement is being performed. In other words, the safety
operation control unit 208 controls the action part 209 such that the
speed of the action part 209 does not exceed a certain speed in the case
where it is determined by the preparatory movement determination unit 203
that the preparatory movement is being performed.

[0102] It should be noted that the safety operation control unit 208 may
stop the action part 209 in the case where it is determined by the
preparatory movement determination unit 203 that the preparatory movement
preceding the dangerous movement is being performed.

[0103] Next, a scene in which the above described safety device 10 is used
will be described. First, a scene in which a press work is performed in
the machine press will be described with reference to FIGS. 5A and 5B.

[0104]FIG. 5A shows a scene in which the worker 100 is setting a work
object W on a press position. Moreover, FIG. 5B shows a scene in which
the machine press is processing the work object W.

[0105] In FIG. 5A, the worker 100 is setting the work object W on the
press position. In this case, parts of the hands and arms of the worker
100 reach a dangerous area 120. However, the worker 100 is not caught in
the action part 209 because the action part 209 is at a standstill.

[0106] Meanwhile, in FIG. 5B, the action part 209 of the machine press is
in operation. In other words, the machine press is in a state in which a
press work is being performed for the work object W. However, since the
body of the worker 100 is not in the dangerous area 120, the body of the
worker 100 is not caught in the action part 209. Generally, the press
work for the work object W is started after the worker 100 reaches a
position a predetermined distance away from the dangerous area 120.

[0107] However, the worker 100 sometimes causes the upper body to lean
over the dangerous area 120 in order to confirm the state of the work
object W during the operation of the action part 209 of the machine
press. In other words, during the press work, there is a case where the
worker 100 brings part of the body closer to the dangerous area 120 as
shown in FIG. 5A.

[0108] In this case, the infrared sensor 204 installed around the
dangerous area 120 detects that part of the body of the worker 100 has
entered the detection area 130 which is larger than the dangerous area
120. Then, the infrared sensor 204 transmits, to the entry detection unit
206, a detection signal indicating the detection of the body of the
worker 100.

[0109] The entry detection unit 206 determines that the body of the worker
100 is entering the detection area in the case where the detection signal
is received from the infrared sensor 204. The safety operation control
unit 208 transmits a stop control signal to the action part 209 in the
case where it is determined that the body of the worker 100 is entering
the detection area 130. As a result, the action part 209 comes to a stop.

[0110] In this way, in the case where part of the body of the worker 100
has entered the detection area 130, the machine press suspends the work
for preventing the worker 100 from being injured. However, in the case
where the body of the worker 100 is approaching the dangerous area 120 at
a speed that is faster than initially estimated, there is a case where
the action part 209 is too late to stop.

[0111] Therefore, in order to avoid being too late for the action part 209
to stop, it can be considered that the detection area 130 is sufficiently
widened. However, in the case where the detection area 130 is widened,
the action part 209 comes to a stop when the worker 100 is only a bit
closer to the machine press. In other words, the safety device 10 causes
the action part 209 to stop even when the body of the worker 100 does not
enter the dangerous area 120. Therefore, the working efficiency of the
machine tool is decreased.

[0112] Therefore, in the present embodiment, the safety of the worker 100
is ensured by determining that the preparatory movement preceding the
dangerous movement is being performed and by avoiding widening the scope
of the detection area.

[0113] Hereafter, the preparatory movement of the worker 100 preceding the
dangerous movement will be described.

[0114] A movement in which the worker 100 brings part of the body closer
to the dangerous area 120 (dangerous movement) is a movement consciously
performed by the worker 100. A typical example of the dangerous movement
is a movement of replacing the work object W or a movement of changing
the position of the work object W with the use of at least one of the
upper limbs. Furthermore, the dangerous movement includes a movement of
removing the work object W on the machine press, a movement of putting
the work object W on the machine press, or a movement of shifting or
rotating the position of the work object W on the machine press with the
use of at least one of the upper limbs. Moreover, the dangerous movement
includes a movement in which, for a maintenance work for the machine
press or the like, the worker 100 puts the right hand or the left hand on
the lower slide or a surrounding area of the lower slide, or a movement
in which the worker 100 leans the lumbar region or the buttock region
against the lower slide or a surrounding area of the lower side.

[0115] Actually, the movement in which the worker 100 brings part of the
body closer to the dangerous area 120 is performed by several stages. For
example, assume that decision-making for correcting the position of the
work object W is made by the worker who is standing near the dangerous
area of the front face of the machine press and is directing the body
toward the machine press.

[0116] In this case, in order to realize the correction of the position of
the work object W, the motion of both arms and the upper body is
determined. After the motion of both arms and the upper body is
determined, in order to adjust a posture for withstanding a change in the
weight balance of the body caused by the motion of both arms and the
upper body, the motion of the back muscles and abdominal muscles which
moves the center of gravity of the lumbar region and the motion of
muscles around the pelvis which adjusts an angle of the lumbar region
against legs are determined. As a result, a knee angle is larger and the
buttock region shifts to the back side.

[0117] Here, the change in the weight balance of the body will be
described. The case will be described as an example where a movement is
started from a state in which the worker is standing upright and pulling
both arms down. First, the body is naturally balanced in a state in which
the worker is standing upright and pulling both arms down, as shown in
(a) of FIG. 6. If the worker puts both arms forward as shown in (c) of
FIG. 6 while the body is balanced in this way, the center of gravity of
whole body of the worker is shifted forward by the weight of both arms.
As a result, the body loses its balance and leans forward, and therefore
the worker cannot keep standing upright.

[0118] Therefore, the worker, as shown in (b) of FIG. 6, shifts the center
of gravity in an orientation for making up for in advance a shift of the
center of gravity by the weight of both arms (that is, an orientation
which is toward the back of the worker and opposite to the working area
of the action part that the worker is trying to extend the arms) and is
prepared for a change in the weight balance caused by the raising of both
arms.

[0119] Therefore, as shown in (b) of FIG. 6, the worker pulls back the
lumbar region without moving the grounding positions of both feet such
that the center of gravity is shifted backward with safety. By pulling
back the lumbar region and shifting the center of gravity of the body
backward, the worker can shift the center of gravity backward without a
backward shift of hand pivot points when extending the arms forward, and
therefore the worker does not have to shift the working position in which
the worker initially intended to work by extending the arms forward.

[0120] The movement of pulling back the lumbar region, as shown in (b) of
FIG. 6, is a movement in which the worker extends the knee bending angle
and shifts the buttock region to the back side. With the movement, the
center of gravity is shifted to the side opposite to the back side of the
worker, that is, the working area of the action part which the worker is
trying to extend the arms forward. Following the movement, the worker
extends the arms to the working area ahead. As a result, as shown in (c)
of FIG. 6, the center of gravity of whole body of the worker is shifted
to the same position as that in which the worker is standing upright or
to a further front position.

[0121] The movement of increasing the knee angle and shifting the buttock
region to the back side in this way corresponds to the preparatory
movement preceding the dangerous movement. The preparatory movement is
unintentionally performed. After the preparatory movement is performed,
the conscious movement by the worker 100 is performed in which the
position of the work object W is corrected by the motion of both arms and
the lumbar region.

[0122] As described above, in the case where a person consciously performs
a movement, the preparatory movement for adjusting a posture is
unintentionally performed before the conscious movement. Body regions
which perform a motion for the preparatory movement tend to be a body
region different from those which perform the motion for the conscious
movement.

[0123] Especially, in the case where the conscious movement is performed
by the large motion of the upper limbs as shown in the above described
dangerous movement, the preparatory movement preceding the conscious
movement is performed by the motion of the lower body which is centered
on the lumbar region and the legs.

[0124] Therefore, the safety device 10 according to the present embodiment
detects with high accuracy that the body of the worker 100 is about to
enter the dangerous area before the entry of the body of the worker 100
into the dangerous area, by using the preparatory movement preceding the
dangerous movement.

[0125] Hereafter, the determination processes for the preparatory movement
by the safety device 10 will be described in detail.

[0126] The posture obtainment unit 201 obtains a plurality of posture data
indicating the posture of the worker 100 in a distance in which the
worker 100 can enter the dangerous area of the machine press.
Specifically, the posture obtainment unit 201 obtains the plurality of
posture data indicating the posture of the lower body of the worker 100
(at least one of the left and right legs and the left and right feet).

[0127] Here, the posture obtainment unit 201 obtains the plurality of
posture data from a pressure sensor sheet 211 which is installed on the
floor surface ahead of the machine press. The pressure sensor sheet 211
measures a pressure distribution of the soles of feet of the worker 100
who is positioned in front of the machine press, and transmits, as the
plurality of posture data, the measured result to the posture obtainment
unit 201.

[0128] For example, as shown in FIG. 6, in the case where the dangerous
movement is performed in which the worker brings the upper body closer to
the dangerous area, a center-of-gravity position 601 of the pressure
distribution of the soles of feet is moved in a direction opposite to the
direction of the machine press ((b) of FIG. 6). The shift of the
center-of-gravity position is caused by the preparatory movement
preceding the dangerous movement. Then, the pressure sensor sheet 211
measures the pressure distribution of the soles of feet of the worker
100.

[0129] Specifically, as shown in FIG. 7, the pressure sensor sheet 211
includes 72 pressure sensors (P11, P12, P13, . . . , and P89) arranged in
a matrix. Each of the pressure sensors measures pressure in each of the
arranged location. Specifically, as shown in FIG. 8, each of the 72
pressure sensors measures a pressure value in a predetermined time
interval (for example, around 10 ms).

[0130] The posture obtainment unit 201 calculates the center-of-gravity
position of the pressure distribution measured by the pressure sensor
sheet 211. Specifically, the posture obtainment unit 201 calculates the
center-of-gravity position (Xg, Yg) as indicated in Expression 1.

[Math. 1]

Xg = Px × Wxy Wxy Yg = Py × Wxy
Wxy ( Expression 1 ) ##EQU00001##

[0131] Here, Px denotes a position in the X direction. Here, Py denotes a
position in the Y direction. Moreover, Wxy denotes a pressure value
measured at position (Px, Py). The posture obtainment unit 201 transmits
the calculated center-of-gravity position to the preparatory movement
determination unit 203. It should be noted that a negative orientation in
the X direction corresponds to an orientation away from the working area
of the action part.

[0132] Next, the preparatory movement determination unit 203 calculates a
moving speed of the center-of-gravity position. Then, the preparatory
movement determination unit 203 determines whether or not the preparatory
movement is being performed with reference to a preparatory movement
definition table 202a stored in the preparatory movement definition
storage unit 202.

[0134] The preparatory movement definition table 202a of FIG. 9 shows that
in the case where a distance from the machine press to the feet of the
worker is from 500 mm to 800 mm and the moving speed of the
center-of-gravity position in the X direction is -10 to -5 mm/s, the
worker is performing a preparatory movement preceding a dangerous
movement. In other words, the preparatory movement definition table 202a
shows that in the case where the moving speed of the center-of-gravity
position in an orientation away from the action part 209 (negative
orientation in X direction) is from greater than or equal to the first
threshold value (5 mm/s) to less than the second threshold value (10
mm/s), the preparatory movement preceding the dangerous movement is being
performed.

[0135] Then, the preparatory movement definition table 202a shows that 500
ms after the preparatory movement, the upper body of the worker enters
the dangerous area. In this way, the preparatory movement definition
table 202a stores the first threshold value and the second threshold
value regarding the moving speed of the center-of-gravity position for
determining whether or not the preparatory movement of the lower body is
being performed before the dangerous movement of the upper body
approaching the dangerous zone of the machine press is performed.

[0136] Therefore, the preparatory movement determination unit 203
determines whether or not the worker 100 is performing the preparatory
movement by comparing the moving speed of the center-of-gravity position
calculated from the plurality of posture data obtained from the posture
obtainment unit 201 with the first threshold value and the second
threshold value stored in the preparatory movement definition table 202a.
The preparatory movement determination unit 203 outputs, to the safety
operation control unit 208, a signal indicating the determination result
when it is determined that the preparatory movement is being performed.

[0137] For example, as shown in FIG. 10, a coordinate of the
center-of-gravity position of the pressure distribution of the soles of
feet of the worker (hereafter, referred to as center-of-gravity
coordinate) is inputted every 10 msec into the preparatory movement
determination unit 203 from the posture obtainment unit 201.

[0138]FIG. 10 shows an example of the center-of-gravity coordinate
inputted every 10 msec from 15 minutes and 20.130 seconds and the
center-of-gravity moving speed calculated from the center-of-gravity
coordinate. It should be noted that here, the case will be described
where it is already known that a distance from the machine press to the
soles of feet ranges from 500 to 800 mm.

[0139] The center-of-gravity moving speed in an X direction is greater
than -5 mm/s at times from 15 minutes and 20.130 seconds to 15 minutes
and 20.170 seconds. In other words, the moving speed of the
center-of-gravity position in an orientation away from the action part
209 (negative orientation of X direction) is less than the first
threshold value (here, "5"). Therefore, the preparatory movement
determination unit 203 determines that the preparatory movement is not
being performed.

[0140] Furthermore, when time advances to 16 minutes and 32.440 seconds,
the center-of-gravity moving speed in the X direction reaches -5 mm/s
which is indicated in a preparatory movement ID "001" in FIG. 9. In other
words, the moving speed of the center-of-gravity position in an
orientation away from the action part 209 (negative orientation of X
direction) is from greater than or equal to the first threshold value
(here, "5") to less than the second threshold value (here, "10").
Therefore, the preparatory movement determination unit 203 determines
that the preparatory movement is being performed.

[0141] The preparatory movement determination unit 203 outputs, to the
safety operation control unit 208, a signal indicating the determination
result. The safety operation control unit 208 slows down the action part
209 when it is determined by the preparatory movement determination unit
203 that the preparatory movement is being performed.

[0142] The operations of the above described safety device 10 will be
described with reference to the flowchart of FIG. 11.

[0143] First, the safety operation control unit 208 determines whether or
not the action part 209 is operating (S901). In the case where the action
part 209 is not operating (NO in S901), a process of Step S901 is
repeated. Meanwhile, in the case where the action part 209 is operating
(YES in S901), the entry detection unit 206 detects, by using a signal
from the infrared sensor 204, whether or not the worker is entering the
detection area (S902).

[0144] In the case where the worker is entering the detection area (YES in
S902), the safety operation control unit 208 stops the action part 209
(S903) and then ends the process.

[0145] Meanwhile, in the case where the worker is not entering the
detection area (NO in S902), the safety operation control unit 208
determines whether or not the action part 209 is operating at a high
speed (S904). Specifically, the safety operation control unit 208
determines whether or not the action part 209 is operating at a speed
greater than or equal to a predetermined speed.

[0146] Here, in the case where the action part 209 is operating at a high
speed (YES in S904), the safety device 10 performs the following
determination processes (S905 to S908). For example, in the case where
the action part 209 is operating at a speed greater than or equal to 200
mm/sec, it take time to cause the action part 209 to stop. Therefore, in
the case where the action part 209 is operating at a speed greater than
or equal to a predetermined speed, the safety device 10 determines
whether or not the preparatory movement is being performed and then
controls the action part 209 according to the determination result.

[0147] Meanwhile, in the case where the action part 209 is not operating
at a high speed (NO in S904), the flow returns to the process of Step
S902. This is because, for example, in the case where the action part 209
is operating at a speed less than 200 mm/sec, it does not take time to
cause the action part 209 to stop. In other words, even if the action
part 209 is caused to stop after an entry into the detection area is
detected by the infrared sensor 204, the possibility is low that the
worker is injured.

[0148] Here, the determination processes for the preparatory movement
(S905 to S908) will be described. In the case where it is determined that
the action part 209 is operating at a high speed (YES in S904), the
posture obtainment unit 201 obtains a plurality of posture data including
the pressure distribution of the soles of feet of the worker 100 (S905).
Specifically, the posture obtainment unit 201, for example, obtains the
pressure distribution of the soles of feet of the worker 100 measured by
the pressure sensor sheet 211. Then, the posture obtainment unit 201
calculates the center-of-gravity position of the obtained pressure
distribution.

[0149] Then, the preparatory movement determination unit 203 calculates a
moving speed of the center-of-gravity position in an orientation away
from the dangerous area (S906). Then, the preparatory movement
determination unit 203 determines whether or not the preparatory movement
preceding the dangerous movement is being performed, by determining
whether or not the calculated moving speed of the center-of-gravity
position meets a condition stored in the preparatory movement definition
storage unit 202 (S907).

[0150] Specifically, the preparatory movement determination unit 203
determines that the preparatory movement preceding the dangerous movement
is being performed in the case where the calculated moving speed of the
center-of-gravity position is from greater than or equal to the first
threshold value to less than the second threshold value. Conversely, the
preparatory movement determination unit 203 determines that the
preparatory movement preceding the dangerous movement is not being
performed in the case where the calculated moving speed of the
center-of-gravity position is less than the first threshold value, or
greater than or equal to the second threshold value.

[0151] Here, in the case where it is determined that the preparatory
movement is not being performed (NO in S907), the flow returns again to
the process of Step S905. Meanwhile, in the case where it is determined
that the preparatory movement is being performed (YES in S907), the
determination result is outputted to the safety operation control unit
208.

[0152] Then, the safety operation control unit 208 controls such that the
action part 209 is not operating at a speed greater than the
predetermined speed (S908) because there is a possibility that the body
of the worker enters the dangerous area a predetermined time later (for
example, 200 msec later). In other words, the safety operation control
unit 208 slows down the action part 209 which is operating at a high
speed.

[0153] As described above, the safety device 10 according to the present
embodiment can cause the action part 209 to slow down or stop in the case
where it is determined that the worker is performing the preparatory
movement preceding the dangerous movement such as one in which the worker
is entering the dangerous area. Therefore, the safety device 10 can
prevent the worker from being injured.

[0154] Moreover, the safety device 10 according to the present embodiment
can determine, by using a change in the posture of the lower body of the
worker, that the preparatory movement preceding the dangerous movement
which brings the upper body of the worker closer to the working area of
the action part is being performed. The preparatory movement is a
movement which is unintentionally performed by a person before the person
performs a conscious movement. In other words, the worker unintentionally
performs the preparatory movement before the dangerous movement which is
a conscious movement. Therefore, by determining that the preparatory
movement is being performed, it is possible to detect with high accuracy
that a dangerous movement is performed before the dangerous movement is
performed.

[0155] Moreover, the safety device 10 can determine whether or not the
preparatory movement is being performed, by using the position specified
by the pressure distribution of the soles of feet of the worker. In other
words, it is possible to detect that the worker is shifting the center of
gravity of whole body of the worker in an orientation away from the
working area of the action part, by using a shift of the position
specified by the pressure distribution of the soles of feet of the
worker. Therefore, it is possible to determine with relative ease that
the preparatory movement preceding the dangerous movement is being
performed.

[0156] Moreover, the safety device 10 can determine whether or not the
preparatory movement is being performed, by using the center-of-gravity
position specified by the pressure distribution of the soles of feet of
the worker. The preparatory movement is a movement for controlling the
posture and therefore is accompanied by the shift of the center of
gravity of whole body of the worker. Therefore, it is possible to
determine with higher accuracy that the preparatory movement preceding
the dangerous movement is being performed, by using the center-of-gravity
position of the pressure distribution of the soles of feet of the worker.

[0157] Moreover, the safety device 10 can determine that the preparatory
movement is being performed in the case where a moving speed, a moving
time, or a moving distance of the center-of-gravity position in an
orientation away from the working area of the action part is greater than
or equal to the first threshold value. In other words, it is possible to
prevent an erroneous determination that the preparatory movement is being
performed in the case where the shift of the center-of-gravity position
in an orientation away from the working area of the action part is a
small shift different from the shift caused by the preparatory movement.
Therefore, it is possible to determine with higher accuracy that the
preparatory movement preceding the dangerous movement is being performed.

[0158] Moreover, the safety device 10 can determine that the preparatory
movement is being performed in the case where a moving speed, a moving
time, or a moving distance of the center-of-gravity position in an
orientation away from the working area of the action part is less than
the second threshold value. In other words, it is possible to prevent an
erroneous determination that the preparatory movement is being performed
in the case where the shift of the center-of-gravity position in an
orientation away from the working area of the action part is a great
shift different from the shift caused by the preparatory movement.
Therefore, it is possible to determine with higher accuracy that the
preparatory movement preceding the dangerous movement is being performed.

[0159] It should be noted that in the present embodiment, the preparatory
movement determination unit 203 determines whether or not the preparatory
movement is being performed by using both the first threshold value and
the second threshold value, but whether or not the preparatory movement
is being performed may be determined by using one of the first threshold
value and the second threshold value.

Embodiment 2

[0160] A safety device 10 according to Embodiment 2 further determines
whether or not the preparatory movement is being performed, by using a
distance between the working area of the action part and the worker, a
body orientation of the worker, and a body size of the worker. With this,
the safety device 10 can determine with high accuracy whether or not the
preparatory movement is being performed also in a machine tool which
handles a large work object. Hereafter, the safety device 10 according to
the present embodiment will be described with reference to the drawings.

[0161]FIG. 12 shows a scene in which the worker 100 is setting a work
object W on a press position. As shown in FIG. 12, a pressure sensor
sheet 311 according to the present embodiment has a greater area than the
pressure sensor sheet according to Embodiment 1. In other words, the
pressure sensor sheet 311 can measure pressure in a wide area.

[0162]FIG. 13 is a block diagram of the safety device 10 of a machine
tool according to Embodiment 2. It should be noted that in FIG. 13,
descriptions of processing units which have the same functions as those
in FIG. 4 will be omitted.

[0164] A distance detection unit 234 detects a distance between the
working area of the action part 209 and the worker 100. In the present
embodiment, the distance detection unit 234 detects, as a distance
between the working area of the action part 209 and the worker 100, a
distance between the machine press and the feet of the worker 100, based
on a pressure distribution measured by the pressure sensor sheet 311.
Specifically, the distance detection unit 234 detects, as a distance
between the working area of the action part 209 and the worker 100, a
distance from the position nearest the machine press among the positions
in which positive pressure is measured by the pressure sensor sheet 311
to the machine press.

[0165] The size detection unit 235 detects a size of at least part of the
worker's body. In the present embodiment, the size detection unit 235
detects the size of the soles of feet of the worker based on a pressure
distribution obtained by the posture obtainment unit 201.

[0166] It should be noted that the size detection unit 235 does not
necessarily have to detect the size of the soles of feet of the worker.
For example, the size detection unit 235 may detect the body height of
the worker based on a captured image of the worker or the like.

[0167] The correction value storage unit 236 is a storage device such as a
memory. In the correction value storage unit 236, a correction value
which is obtained from the body size of the worker detected by the size
detection unit 235 is stored.

[0168] The correction unit 237 corrects a distance detected by the
distance detection unit 234 based on the size detected by the size
detection unit 235. Specifically, the correction unit 237 corrects the
detected distance such that when a size of at least part of the worker's
body is larger, the distance is shorter.

[0169] This is because a possibility that the worker enters the dangerous
area is varied according to the body size of the worker. In other words,
even if the distance from the dangerous area is the same, a worker with a
large body is more likely to enter the dangerous area than a worker with
a small body. Therefore, the correction unit 237 corrects a distance
detected by the distance detection unit 234 according to the size
detected by the size detection unit 235.

[0170] The following shows an example of a correction method.

[0171] Among a plurality of pressure sensors owned by the pressure sensor
sheet 311, the size detection unit 235 extracts, as a group of pressure
sensors corresponding to the area of the soles of feet of the worker, a
group of pressure sensors which are mutually adjacent and in which
positive pressure values are measured. For example, the size detection
unit 235 extracts a group of pressure sensors which are depicted by
hatching and correspond to each of the left and right foot areas of the
worker in FIG. 14.

[0172] Then, the size detection unit 235 calculates, as a major axis
length L of the soles of feet of the worker 100, a distance between two
sensors which are most distant with each other, in at least one group of
the extracted pressure sensors. In FIG. 14, the size detection unit 235
calculates a distance between a pressure sensor Px1y1 and a pressure
sensor Px2y2. Here, since the mutually adjacent pressure sensors are 30
mm away from each other, the major axis length L is calculated as
Expression 2.

[0174] Then, the size detection unit 235 calculates L/Ls which is a ratio
of the major axis length L to a standard major axis length Ls which is
determined in advance. In the case where the standard major axis length
Ls is 280 mm, for example, the size detection unit 235 calculates that
L/Ls which is the ratio of the major axis length L to the standard major
axis length Ls is 0.921 (=258/280). Then, the size detection unit 235
stores the calculated ratio as a correction value in the correction value
storage unit 236.

[0175] Therefore, the correction unit 237 corrects a distance detected by
the distance detection unit 234 with the use of the correction value
stored in the correction value storage unit 236. Specifically, the
correction unit 237 outputs, as a distance after correction, a value
which is produced by division of the distance detected by the distance
detection unit 234 by the correction value (0.921) to the preparatory
movement determination unit 203. In other words, the correction unit 237
corrects the distance such that when the size of the soles of feet of the
worker is larger, the distance is shorter.

[0176] In this example, the correction unit 237 corrects the distance such
that the distance from the worker 100 to the dangerous area 120 is longer
than the actual distance, because the size of the soles of feet of the
worker 100 is smaller than the standard level. Conversely, in the case
where the size of the soles of feet of the worker 100 is larger than the
standard level, the distance from the worker 100 to the dangerous area
120 is corrected to be shorter than the actual distance.

[0177] The orientation detection unit 233 detects a body orientation of
the worker. Specifically, the orientation detection unit 233 detects a
degree of an angle of the worker's front body with respect to the front
face of the machine press from a form of an area of the pressure sensors
which are mutually adjacent and in which positive pressure values are
measured.

[0178] The following shows an example of a method of detecting a body
orientation of the worker.

[0179] First, the orientation detection unit 233 identifies two sensors
which are most distant from each other in each of the groups of pressure
sensors which are mutually adjacent and in which positive pressure values
are measured. The two sensors specified in this way are mostly located
under the tiptoes and the heels. In FIG. 14, two pressure sensors (Px1y1,
Px2y2) corresponding to the right foot and two pressure sensors (Px3y3,
Px4y4) corresponding to the left foot are specified.

[0180] Then, the orientation detection unit 233 detects, as a body
orientation of the worker, an orientation of a vector which connects (i)
a midpoint of a line segment connecting a pressure sensor under the right
heel and a pressure sensor under the left heel and (ii) a midpoint of a
line segment connecting a pressure sensor under the right tiptoe and a
pressure sensor under the left tiptoe. The orientation of the vector
detected in this way can be represented by a ratio of a distance in an X
direction and a distance in a Y direction.

[0181] In the example of FIG. 14, a coordinate of the midpoint of the line
segment connecting the pressure sensor under the right heel and the
pressure sensor under the left heel is P((x1+x3)/2, (y1+y3)/2). Moreover,
a coordinate of the midpoint of the line segment connecting the pressure
sensor under the right tiptoe and the pressure sensor under the left
tiptoe is P((x2+x4)/2, (y2+y4)/2). When a coordinate of the pressure
sensor located in the upper left of FIG. 14 is (1, 1), the coordinates of
these midpoints are (4, 9) and (10, 3.5), respectively. Therefore, the
distance in the X direction is 6, and the distance in the Y direction is
5.5.

[0182] Here, the orientation detection unit 233 detects a value which is
produced by the division of the distance in the Y direction by the
distance in the X direction (5.5/6=0.917) as angle information indicating
an angle formed between the body orientation of the worker and the
orientation of the working area of the action part seen from the worker.
Here, in the case where an angle formed between the body orientation of
the worker and the orientation of the working area of the action part
seen from the worker is represented as θ, a value which is produced
by the division of the distance in the Y direction by the distance in the
X direction corresponds to tan θ. The orientation detection unit
233 outputs the detected angle information to the preparatory movement
determination unit 203.

[0183] It should be noted that there is a case where the pressure
distribution for each of the soles of feet measured by the pressure
sensor sheet 311 is not only one area as shown in the example of FIG. 14
but also divided into a plurality of areas, depending on each of the shoe
sole forms. For example, as shown in FIG. 15, the pressure distribution
for each of the soles of feet is divided into two areas because between
the heel side and the tiptoe side, there is an area to which no pressure
is applied. In this case, the size detection unit 235 and the orientation
detection unit 233 may extract, as a group of pressure sensors, a group
of pressure sensors corresponding to the tiptoe and a group of pressure
sensors corresponding to the heel by holding a plurality of kinds of
pressure distributions and by performing a matching between a pressure
distribution measured by the pressure sensor sheet 311 and each of the
held pressure distribution patterns.

[0184] The preparatory movement definition storage unit 202 stores, in
association with a plurality of distances between the working area of the
action part and the worker, a plurality of pairs of the first threshold
value and the second threshold value. Furthermore, the preparatory
movement definition storage unit 202 stores, in association with a
plurality of distances between the working area and the worker, a
plurality of third threshold values regarding the body orientation.

[0185] For example, as shown in FIG. 16, the preparatory movement
definition storage unit 202 stores, in association with the distance, the
preparatory movement definition table 202a which includes the body
orientation, the center-of-gravity moving speed in an X direction, a
relative time in which an entry into the dangerous area is predicted, and
an entry portion.

[0186] A preparatory movement ID001 of FIG. 16 indicates that the
preparatory movement preceding the dangerous movement is being performed
in the case where a distance between the machine press and the worker's
feet is from 500 to 800 mm, a value which is produced by the division of
the distance in the Y direction by the distance in the X direction is
less than 0.26, and the center-of-gravity moving speed is from -10 to -5
mm/s. It should be noted that 0.26 which is the value produced by the
division of the distance in the Y direction by the distance in the X
direction corresponds to the fact that a body orientation of the worker
with respect to the front face of the machine press is 15 degrees.

[0187] When such a condition is met, it is shown that the upper body of
the worker enters the dangerous area 500 msec later. In this way, in the
preparatory movement definition storage unit 202, information about the
preparatory movement of the lower body preceding the dangerous movement
which causes the upper body to enter the dangerous area is stored.

[0188] The preparatory movement determination unit 203 determines whether
or not the preparatory movement preceding the dangerous movement is being
performed by determining whether or not the condition indicated by the
preparatory movement definition table 202a is met.

[0189] Specifically, the preparatory movement determination unit 203
identifies, with reference to the preparatory movement definition table
202a, a condition of the center-of-gravity moving speed and a body
orientation that corresponds to a distance corrected by the correction
unit 237. Specifically, the preparatory movement determination unit 203
identifies the range of the center-of-gravity moving speed (the first
threshold value to the second threshold value) and the range of a body
orientation that correspond to the corrected distance.

[0190] Then, the preparatory movement determination unit 203 determines
whether or not the center-of-gravity moving speed obtained from the
plurality of posture data is within the range of the specified
center-of-gravity moving speed. Furthermore, the preparatory movement
determination unit 203 determines whether or not the value indicating
angle information detected by the orientation detection unit 233 is
within the range of the specified body orientation.

[0191] Here, in the case where the center-of-gravity moving speed is
within the range of the specified center-of-gravity moving speed and the
value indicating angle information is within the range of the specified
body orientation, the preparatory movement determination unit 203
determines that the preparatory movement preceding the dangerous movement
is being performed.

[0192] Next, operations of the safety device 10 as configured the above
will be described.

[0193] FIG. 17 is a flowchart showing the operations of the safety device
10 according to Embodiment 2. The same steps as those in FIG. 11 are
provided with the same signs and their descriptions will be omitted.

[0194] After the plurality of posture data including the pressure
distribution of the soles of feet of the worker are obtained (S905), the
size detection unit 235 determines whether or not there is a worker on
the pressure sensor sheet 311 (S101). Specifically, the size detection
unit 235, for example, determines whether or not there is a worker on the
pressure sensor sheet 311 by determining whether or not the number of
pressure sensors which measure positive pressure values is more than a
constant number.

[0195] In the case where there is not a worker on the pressure sensor
sheet 311 (NO in S101), the size detection unit 235 deletes the
correction value stored in the correction value storage unit 236 (S102)
and the flow returns to the process of Step S902.

[0196] In the case where there is a worker on the pressure sensor sheet
311 (YES in S101), the size detection unit 235 determines whether or not
a correction value is stored in the correction value storage unit 236
(S103). Here, in the case where a correction value is not stored (NO in
S103), the size detection unit 235 detects the size of the soles of feet
of the worker by using the pressure distribution of the soles of feet of
the worker included in the plurality of posture data, and stores, as a
correction value, the ratio of the detected size to the standard size in
the correction value storage unit 236 (S104). Meanwhile, in the case
where a correction value is stored (YES in S103), the distance detection
unit 234 detects a distance between the worker and the dangerous area.
Then, the correction unit 237 corrects the detected distance with the use
of the correction value stored in the correction value storage unit 236.
(S106)

[0197] Furthermore, the orientation detection unit 233 detects the body
orientation of the worker with respect to the front face of the machine
press (S107). Then, the preparatory movement determination unit 203
calculates the moving speed of the center-of-gravity position of the
worker (S906).

[0198] The preparatory movement determination unit 203 determines whether
or not the preparatory movement is being performed by determining whether
or not the body orientation of the worker and the center-of-gravity
moving speed are within a range which is stored by the preparatory
movement definition storage unit 202 and which corresponds to a distance
after correction (S907).

[0199] As described above, the safety device 10 according to the present
embodiment can determine whether or not the preparatory movement
preceding the dangerous movement in which the worker enters the dangerous
area is being performed, by using the body size of the worker and the
body orientation of the worker. With this, the preparatory movement
preceding the dangerous movement can be determined with high accuracy.
Moreover, in the case where it is determined that the preparatory
movement is being performed, the action part can be slowed down or
stopped and the worker can be prevented from being injured.

[0200] Specifically, the safety device 10 can correct the distance between
the working area of the action part and the worker such that when at
least a size of part of the worker's body is larger, the distance is
shorter. When the body size of the worker is larger, the possibility is
higher that the body enters the working area of the action part even
though the worker is at a position away from the working area of the
action part. Therefore, by determining whether or not the preparatory
movement preceding the dangerous movement is being performed based on a
distance which is corrected according to the body size of the worker, it
can be determined with higher accuracy the preparatory movement preceding
the dangerous movement is being performed.

[0201] Moreover, the safety device 10 can determine whether or not the
preparatory movement is being performed, based on the body orientation of
the worker. When the orientation of the worker is toward the front face,
the possibility is higher that the body enters the working area of the
action part. Therefore, it is possible to determine with higher accuracy
that the preparatory movement preceding the dangerous movement is being
performed.

[0202] Moreover, the safety device 10 can determine whether or not the
preparatory movement is being performed, based on the first threshold
value and the second threshold value that correspond to the detected
distance. The shift of the center-of-gravity position in an orientation
away from the working area of the action part which is caused by the
preparatory movement is varied by depending on the distance between the
working area of the action part and the worker. For example, the moving
distance of the center-of-gravity position is longer because when the
distance between the working area of the action part and the worker is
longer, the dangerous movement is a larger movement. Therefore, by
determining whether or not the preparatory movement is being performed
based on the first threshold value and the second threshold value that
correspond to the detected distance, it is possible to determine with
higher accuracy that the preparatory movement preceding the dangerous
movement is being performed.

[0203] It should be noted that in Embodiments 1 and 2, the safety device
10 slows down or stops the action part 209 in the case where the
preparatory movement is being performed, but does not necessarily have to
slow down or stop the action part 209. For example, the safety device 10
may output a warning sound in the case where the preparatory movement is
being performed. Moreover, the safety device 10 may turn on a warning
lamp in the case where the preparatory movement is being performed.

[0204] Moreover, the safety device 10 may, after the detection of the
preparatory movement, return a speed of the action part to a level during
a normal operation in the case where entry detection is not performed by
the infrared sensor 204 even after a predetermined entry time is passed.
With this, a decrease in working efficiency caused by an erroneous
determination of the preparatory movement can be prevented.

[0205] As described above, the safety device 10 according to an aspect of
the present disclosure has been described based on the embodiments, but
the present disclosure is not defined only by the embodiments. Various
modifications conceived by those skilled in the art and applied to the
present embodiments or embodiments structured by a combination of
constituent elements in different embodiments are possible without
materially departing from the novel teachings and advantages of this
disclosure. Accordingly, all such modifications are intended to be
included within the scope of the present disclosure.

[0206] For example, in Embodiments 1 and 2, the posture obtainment unit
201 obtains the plurality of posture data from the pressure sensor sheet,
but does not necessarily have to obtain the plurality of posture data
from the pressure sensor sheet. For example, the posture obtainment unit
201 may obtain the plurality of posture data from a posture detection
device which includes one or more cameras and an image recognition
system. In that case, the plurality of posture data are acceptable as
long as the data include a three-dimensional model which indicates a body
shape of the worker. Then, the preparatory movement determination unit
203 may calculate the center-of-gravity position of the lower body of the
worker from the three-dimensional model, and may determine whether or not
the preparatory movement is being performed, based on the moving speed of
the center-of-gravity position and the like.

[0207] It should be noted that in Embodiments 1 and 2, a machine tool is a
machine press which performs a press work by slides which perform an
up-and-down reciprocating motion, but may be a rolling machine using a
roller, a stationary power saw, a polishing machine, a sewing machine, or
the like. A machine tool may be a machine as long as a machine requires
the worker to be in contact with a work object on the machine tool, such
as the case where there is need for replacement and position adjustment
of a work object or for a support of a work object.

[0208] It should be noted that in Embodiments 1 and 2, the safety device
is a safety device of a machine tool which performs a press work for a
work object with the use of slides which perform an up-and-down
reciprocating motion, but does not necessarily have to be a safety device
of the machine tool which performs a work for the work object. For
example, the safety device may be a safety device of a robot which moves
the object.

[0209] The following will describe a safety device of a transportation
robot which performs a shift of heavy goods (object). Here, in the work
of transporting the heavy goods, the worker cooperates with the robot to
transport the heavy goods.

[0210]FIG. 18 is a diagram showing a scene in which the worker 100 and a
robot 401 are carrying out cooperative transportation. In FIG. 18, the
worker 100 cooperates with the robot 401 to transport heavy goods 402 by
putting hands on the heavy goods 402 which is transported by an action
part of the robot 401.

[0211] For example, in the case where a motor is incorporated into a
chassis, the heavy goods 402 correspond to the motor. In this case, the
worker 100 adjusts the position of the action part of the robot 401 or
the motor held by the robot 401 by directly touching the action part of
the robot 401 or the motor held by the robot 401 such that the worker 100
slightly adjusts the position or the orientation of the motor with
respect to the non-illustrated chassis (heavy goods 402).

[0212] In the case where the worker 100 performs such a movement, there is
a possibility that the body of the worker 100 (especially part of the
upper body) collides with the action part of the robot 401 or the heavy
goods 402 which is being transported. Therefore, the safety device
detects, as similarly to the safety device according to Embodiment 1 or
2, for example, a change in the posture of the worker 100 with a pressure
sensor sheet 411 installed on the floor surface of the working position
of the worker 100 and the like. Then, the safety device determines
whether or not the preparatory movement is performed in which the upper
body of the worker 100 is entering a predetermined movable area of the
robot 401.

[0213] In the case where it is determined that the preparatory movement of
the dangerous movement is being performed, the safety device slows down
the speed of the action part of the robot 401 to a speed in which the
worker is not injured even in the case of a collision. Alternately, in
the case where it is determined that the preparatory movement of the
dangerous movement is being performed, the safety device may control the
robot 401 such that an impact of a collision on the worker 100 is eased
by a control of a suspension or a damper, or by a control of robot
operational impedance.

[0214] It should be noted that Embodiments 1 and 2 describe a
configuration in which the preparatory movement of the worker is detected
with the pressure sensor sheet installed on the floor surface by assuming
that the working posture of the worker is an erect position. However, in
the case where the worker is using a work chair or a standing aid for
work, the pressure sensor sheets are provided on the seating surface of
the work chair and the body contact surface of the standing aid and it
may be determined, from a change in the pressure distribution of the
worker's buttock region and femoral region, whether or not the
preparatory movement is being performed.

[0215] It should be noted that in Embodiments 1 and 2, the safety device
10 determines whether or not the preparatory movement is being performed,
based on the shift of the center-of-gravity position of the pressure
distribution of the soles of feet of the worker by the pressure sensor
sheet installed on the floor surface, but does not necessarily have to
determine the performance of the preparatory movement in this way. For
example, the safety device 10 may determine whether or not the
preparatory movement is being performed, based on a change in pressure
applied to each of the areas of the front sides and the back sides with
respect to the worker's plantar arches.

[0216] It should be noted that in Embodiments 1 and 2, the safety device
10 detects the distance between the worker and the dangerous area based
on the positions of pressure sensors in which positive pressure values
are measured, but may detect the distance based on the center-of-gravity
position of the pressure distribution of the soles of feet.

[0217] It should be noted that in Embodiments 1 and 2, the pressure sensor
sheet is installed on the floor surface, but may be installed in the shoe
soles or in the inside bottom surfaces of the shoes. In that case, the
distance between the dangerous area of the machine tool and the worker
may be separately measured by a measurement means which measures a
distance between two points, for example, an ultrasonic sensor, a camera,
or the like.

[0218] It should be noted that in Embodiment 1, the safety device 10 does
not include the distance detection unit 234, but may include the distance
detection unit 234. In that case, the preparatory movement determination
unit 203 may determine that the preparatory movement is being performed
in the case where the center-of-gravity position is shifting in an
orientation away from the working area of the action part and the
distance detected by the distance detection unit 234 is less than the
third threshold value. With this, the preparatory movement determination
unit 203 can determine that the preparatory movement is being performed
in the case where the distance between the working area of the action
part and the worker is less than the third threshold value. In other
words, since the possibility is low that the worker's body enters the
working area of the action part in the case where the worker is at a
position away from the working area of the action part, the preparatory
movement determination unit 203 can determine that the preparatory
movement preceding the dangerous movement is not being performed. In
other words, the safety device 10 can slow down or stop the action part
in the case where the possibility is low that the worker is injured, and
therefore can enhance the workability.

[0219] Moreover, in Embodiments 1 and 2, the preparatory movement
determination unit 203 determines whether or not the preparatory movement
is being performed, based on the moving speed of the center-of-gravity
position, but may determine whether the preparatory movement is being
performed, based on the moving time or the moving distance of the
center-of-gravity position.

[0220] Moreover, in Embodiments 1 and 2, the safety device 10 includes a
plurality of constituent elements as shown in FIG. 4 or 13, but does not
necessarily have to include all of the constituent elements.
Specifically, the safety device 10, for example, as shown in FIG. 19, may
be a device which includes the posture obtainment unit 201 and the
preparatory movement determination unit 203. Even in this case, the
safety device 10 can determine that the preparatory movement preceding
the dangerous movement which brings the upper body of the worker closer
to the working area of the action part is being performed, based on a
change in the posture of the lower body of the worker. Therefore, the
safety device 10 can detect with high accuracy that the dangerous
movement is performed before the dangerous movement is performed.
Furthermore, the safety device 10 can prevent the worker from being
injured by outputting a determination result to the safety operation
control unit 208 or the like.

[0221] Moreover, part or the whole of the constituent elements included in
the safety device according to Embodiment 1 or 2 may be composed of one
system Large Scale Integration (LSI). For example, the safety device 10
may be composed of a system LSI including the posture obtainment unit 201
and the preparatory movement determination unit 203.

[0222] The system LSI is a super-multi-function LSI which is manufactured
by integrating constituent units on one chip, and is specifically a
computer system which is configured by including a microprocessor, Read
Only Memory (ROM), Random Access Memory (RAM), and the like. A computer
program is stored in the RAM. The system LSI achieves its function
through an operation of the microprocessor according to the computer
program.

[0223] It should be noted that the name used here is system LSI, but may
be called Integrated Circuit (IC), LSI, super LSI or ultra LSI, depending
on a difference in the degree of integration. Moreover, the means for
circuit integration is not limited to an LSI, and an implementation with
a dedicated communication circuit or a general-purpose processor is also
available. In addition, it is also acceptable to use a Field Programmable
Gate Array (FPGA) that is programmable after the LSI has been
manufactured, and a reconfigurable processor in which connections and
settings of circuit cells within the LSI are reconfigurable.

[0224] Furthermore, if integrated circuit technology that replaces LSI
appears through progress in semiconductor technology or other derived
technology, that technology can naturally be used to carry out
integration of the constituent elements. Application of biotechnology is
one such possibility.

[0225] Moreover, an aspect of the present disclosure may be a preparatory
movement determination method of designating the characteristic
processing units included in the safety device as steps. Moreover, an
aspect of the present disclosure may be also implemented as a computer
program that causes the computer to execute each of the characteristic
steps included in the preparatory movement determination method.
Furthermore, an aspect of the present disclosure may be a
computer-readable non-transitory medium having such a computer program
recorded thereon.

[0226] It should be noted that in each of the embodiments, each of the
constituent elements may be implemented by being composed of a dedicated
hardware or by executing a software program that is suitable to each of
the constituent elements. Each of the constituent elements may be
implemented by having a program execution unit, such as Central
Processing Unit (CPU) or a processor, read and execute a software program
that is recorded on a storage medium such as a hard disk or a
semiconductor memory. Here, the following software can implement an image
decoding device or the like according to each of the embodiments.

[0227] In other words, the program causes a computer to execute the
preparatory movement determination method for preventing the worker from
being injured by a machine which includes an action part for processing
or moving the work object. In other words, the program causes the
computer to execute a posture obtainment step in which the plurality of
posture data indicating a posture at least part of the lower body of the
worker are obtained and a preparatory movement determination step in
which in the case where a change in the posture indicated by the the
plurality of posture data shows that the worker is shifting the center of
gravity of whole body of the worker in an orientation away from the
working area of the action part without moving the positions of both
feet, it is determined that the preparatory movement preceding the
dangerous movement which brings at least part of the upper body of the
worker closer to the working area of the action part is being performed.

INDUSTRIAL APPLICABILITY

[0228] Exemplary devices and methods in the present disclosure and their
equivalents within the scope of the inventive concept defined in the
attached claims are effective as a safety device of a machine tool such
as a machine press which performs a press work by slides which perform an
up-and-down reciprocating motion, a rolling machine to using a roller, a
stationary power saw, a polishing machine, a sewing machine, or the like.